There are many scenarios, but here's a simple one. Boots on the ground.
You have men on the ground who can see the enemy position, they need to know exactly where they are to be able to know exactly where the enemy is. Without GPS you are relying on visual points of reference against maps of shaky providence.
Boots on the ground don't need to be accurate to within 1cm. If a normal human is within 10 meters they can nearly always figure things out. In fact if humans are that close it is because you don't actually know where the enemy is and you need the humans to find them - otherwise you would have a plane drop a bomb on them.
Where you need more accuracy is when you want something at a long distance to do something - drop a bomb or something.
